Technical Field
The present invention relates to reliability testing and, more particularly, to isolating and localizing time dependent dielectric breakdown defects.
Description of the Related Art
Time dependent dielectric breakdown (TDDB) in the back-end-of-line (BEOL) in integrated circuits is a significant source of reliability problems as circuit formation technology reaches 22 nm and beyond. As a result, the performance of interconnection is susceptible to technology shrinking, new material (low-k value) features, and process improvement and development. To better understand the effect, leakage current measurement and emission microscopy tests have been conducted separately. Leakage current measurement demonstrates the evolution of dielectric breakdown times. Extrapolation and interpolation on the measurement results then enable the lifetime analysis of the dielectric and the TDDB effect. Light emission tests have also been used, since photon emission is recognized as occurring via energy states generated by dangling bonds and/or impurities at the material interface, which is tightly related to the TDDB progressive development. However, the detailed mechanism of the TDDB effect is still not clear, for that: (1) the progressive development of TDDB effect is not carefully caught on-site; and (2) all prior analysis was conducted off-line and after the experiments, when the TDDB sites on the device under test (DUT) are totally destroyed. This leads to inaccuracy and insufficient for the further failure analysis, including physical failure analysis and scanning electron microscope; and (3) the correlation between electrical leakage current and photon emission is not studied.